In general, in line with technological development and increasing demands for mobile devices, demands for secondary batteries are also increasing sharply, and, most of all, lithium (ion/polymer) secondary batteries having a high energy density, a high operation voltage, and excellent storage and life characteristics are widely used as an energy source for various electronic products as well as mobile devices.
Korea Patent Publication No. 2009-0065587 discloses a pouch type secondary battery with improved safety, in which a channel is formed in a cell and on a sealing part of an electrode tap. When gas is excessively generated in the pouch to increase pressure due to overcharging, internal short, and the like, the gas may be discharged to the outside of the pouch through the channel. In other words, when the gas in the cell is discharged to the outside, the gas is always discharged through the sealing part of the electrode tap, so that a gas discharge direction may be predicted in advance.
Meanwhile, a reference pressure at which gases inside the pouch type secondary battery are discharged may be varied according to specifications and operation conditions of electronic/mechanical devices on which the pouch type secondary battery is installed. That is, some electronic/mechanical devices need to discharge gases even if an internal gas pressure of the pouch type secondary battery is slightly increased, whereas other electronic/mechanical devices do not need to discharge gases even when the internal gas pressure of the pouch type secondary battery is significantly increased.
However, the disclosed patent is disadvantageous in that, when a gas discharge reference pressure of the pouch type secondary battery required by the respective electronic/mechanical devices is varied, a design for the sealing part should be changed.
It is assumed that a pouch type secondary battery is manufactured according to a gas discharge reference pressure required by a specific electronic/mechanical device and installed on the electronic/mechanical device. However, when the preset gas discharge reference pressure is considered inappropriate for the electronic/mechanical device during operation and thus the gas discharge reference pressure needs to be increased or decreased, there is a limitation in that the existing pouch type secondary battery should be entirely replaced by a pouch type secondary battery having a newly changed gas discharge reference pressure.